This invention relates to an idle air bypass valve for a fuel injected internal combustion engine.
Such a valve is used in an automotive vehicle to control the flow of combustion air into the engine when the engine is idling. Because the load on the engine may vary for any of a number of different reasons while the engine is idling, the idle air bypass valve is required so that the proper amount of combustion air is inducted for all idle conditions. For example, a typical idle air bypass valve placed under the control of the engine control computer may strive to maintain a stable idle speed for the engine irrespective of the load imposed on the engine or of the engine temperature. For example, if the idle load on the engine changes so that there is a resulting change in manifold vacuum, the idle air bypass valve should respond by making a corresponding change in the degree of restriction that it imposes on the idle air flow such that proper air flow for the desired idle operation is maintained.
Heretofore, certain engine idle control strategies have involved anticipatory adjustment of the idle air bypass valve prior to allowing changes in accessory loadings of the engine (i.e., air conditioning load, power steering load, etc.). One object of the present invention is to provide an idle air bypass valve which exhibits a sufficiently fast response that it becomes possible to eliminate such anticipatory adjustments.
Certain known solenoid-actuated idle air bypass valves are mechanically biased to be normally closed and therefore require a certain degree of electrical energization before opening. If the electrical energization is not received by the solenoid, or the solenoid actuator itself fails, opening of the idle air bypass is impossible, and typically the engine cannot be started. Another object of the present invention is to provide an idle air bypass valve which is open at engine starting without the need for electrical power to the valve. A related feature is that in the event of electrical failure of the solenoid-actuator or of the control circuitry to the solenoid, the idle air bypass valve of the invention still permits the passage of some air into the engine so that it is possible that the engine may remain running and therefore be driven to a service facility.
The foregoing, along with additional features and benefits of the invention, will be seen in the ensuing detailed description that is accompanied by a drawing. The drawing discloses an exemplary presently preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.